def normal_pdf(x, mean, var):
    return np.exp(-(x - mean)**2 / (2*var))

# Generate the space in which the blobs will live
xmin, xmax, ymin, ymax = (0, 100, 0, 100)
n_bins = 100
xx = np.linspace(xmin, xmax, n_bins)
yy = np.linspace(ymin, ymax, n_bins)

# Generate the blobs. The range of the values is roughly -.0002 to .0002
means_high = [20, 50]
means_low = [50, 60]
var = [150, 200]

gauss_x_high = normal_pdf(xx, means_high[0], var[0])
gauss_y_high = normal_pdf(yy, means_high[1], var[0])

gauss_x_low = normal_pdf(xx, means_low[0], var[1])
gauss_y_low = normal_pdf(yy, means_low[1], var[1])

weights = (np.outer(gauss_y_high, gauss_x_high) - np.outer(gauss_y_low, gauss_x_low))

# We'll also create a grey background into which the pixels will fade
#greys = np.full((*weights.shape, 3), 70, dtype=np.uint8)

# First we'll plot these blobs using ``imshow`` without transparency.
vmax = np.abs(weights).max()
imshow_kwargs = {
    'vmax': vmax,
    'vmin': -vmax,
    'cmap': 'RdYlBu',
    'extent': (xmin, xmax, ymin, ymax),
}

fig, ax = plt.subplots()
#ax.imshow(greys)
ax.imshow(weights, **imshow_kwargs)
ax.set_axis_off()

# Create an alpha channel of linearly increasing values moving to the right.
alphas = np.ones(weights.shape)
alphas[:, 30:] = np.linspace(1, 0, 70)

# Create the figure and image
# Note that the absolute values may be slightly different
fig, ax = plt.subplots()
#ax.imshow(greys)
ax.imshow(weights, alpha=alphas, **imshow_kwargs)
ax.set_axis_off()

# If applicable, paste the console output here
#
#

Error in callback <function post_execute at 0x7f4972d48578> (for post_execute):
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/pyplot.pyc in post_execute()
    147             def post_execute():
    148                 if matplotlib.is_interactive():
--> 149                     draw_all()
    150 
    151             # IPython >= 2

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/_pylab_helpers.pyc in draw_all(cls, force)
    134         for f_mgr in cls.get_all_fig_managers():
    135             if force or f_mgr.canvas.figure.stale:
--> 136                 f_mgr.canvas.draw_idle()
    137 
    138 atexit.register(Gcf.destroy_all)

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/backend_bases.pyc in draw_idle(self, *args, **kwargs)
   2053         if not self._is_idle_drawing:
   2054             with self._idle_draw_cntx():
-> 2055                 self.draw(*args, **kwargs)
   2056 
   2057     def draw_cursor(self, event):

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/backends/backend_agg.pyc in draw(self)
    435             # if toolbar:
    436             #     toolbar.set_cursor(cursors.WAIT)
--> 437             self.figure.draw(self.renderer)
    438             # A GUI class may be need to update a window using this draw, so
    439             # don't forget to call the superclass.

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/artist.pyc in draw_wrapper(artist, renderer, *args, **kwargs)
     53                 renderer.start_filter()
     54 
---> 55             return draw(artist, renderer, *args, **kwargs)
     56         finally:
     57             if artist.get_agg_filter() is not None:

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/figure.pyc in draw(self, renderer)
   1491 
   1492             mimage._draw_list_compositing_images(
-> 1493                 renderer, self, artists, self.suppressComposite)
   1494 
   1495             renderer.close_group('figure')

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/image.pyc in _draw_list_compositing_images(renderer, parent, artists, suppress_composite)
    139     if not_composite or not has_images:
    140         for a in artists:
--> 141             a.draw(renderer)
    142     else:
    143         # Composite any adjacent images together

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/artist.pyc in draw_wrapper(artist, renderer, *args, **kwargs)
     53                 renderer.start_filter()
     54 
---> 55             return draw(artist, renderer, *args, **kwargs)
     56         finally:
     57             if artist.get_agg_filter() is not None:

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/axes/_base.pyc in draw(self, renderer, inframe)
   2633             renderer.stop_rasterizing()
   2634 
-> 2635         mimage._draw_list_compositing_images(renderer, self, artists)
   2636 
   2637         renderer.close_group('axes')

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/image.pyc in _draw_list_compositing_images(renderer, parent, artists, suppress_composite)
    139     if not_composite or not has_images:
    140         for a in artists:
--> 141             a.draw(renderer)
    142     else:
    143         # Composite any adjacent images together

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/artist.pyc in draw_wrapper(artist, renderer, *args, **kwargs)
     53                 renderer.start_filter()
     54 
---> 55             return draw(artist, renderer, *args, **kwargs)
     56         finally:
     57             if artist.get_agg_filter() is not None:

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/image.pyc in draw(self, renderer, *args, **kwargs)
    592         else:
    593             im, l, b, trans = self.make_image(
--> 594                 renderer, renderer.get_image_magnification())
    595             if im is not None:
    596                 renderer.draw_image(gc, l, b, im)

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/image.pyc in make_image(self, renderer, magnification, unsampled)
    840         return self._make_image(
    841             self._A, bbox, transformed_bbox, self.axes.bbox, magnification,
--> 842             unsampled=unsampled)
    843 
    844     def _check_unsampled_image(self, renderer):

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/image.pyc in _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification, unsampled, round_to_pixel_border)
    520                 alpha_channel = output[:, :, 3]
    521                 alpha_channel[:] = np.asarray(
--> 522                     np.asarray(alpha_channel, np.float32) * out_alpha * alpha,
    523                     np.uint8)
    524 

ValueError: operands could not be broadcast together with shapes (218,218) (100,100) 

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
/xxx/anaconda2/lib/python2.7/site-packages/IPython/core/formatters.pyc in __call__(self, obj)
    332                 pass
    333             else:
--> 334                 return printer(obj)
    335             # Finally look for special method names
    336             method = get_real_method(obj, self.print_method)

/xxx/anaconda2/lib/python2.7/site-packages/IPython/core/pylabtools.pyc in <lambda>(fig)
    245 
    246     if 'png' in formats:
--> 247         png_formatter.for_type(Figure, lambda fig: print_figure(fig, 'png', **kwargs))
    248     if 'retina' in formats or 'png2x' in formats:
    249         png_formatter.for_type(Figure, lambda fig: retina_figure(fig, **kwargs))

/xxx/anaconda2/lib/python2.7/site-packages/IPython/core/pylabtools.pyc in print_figure(fig, fmt, bbox_inches, **kwargs)
    129 
    130     bytes_io = BytesIO()
--> 131     fig.canvas.print_figure(bytes_io, **kw)
    132     data = bytes_io.getvalue()
    133     if fmt == 'svg':

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/backend_bases.pyc in print_figure(self, filename, dpi, facecolor, edgecolor, orientation, format, **kwargs)
   2210                     orientation=orientation,
   2211                     dryrun=True,
-> 2212                     **kwargs)
   2213                 renderer = self.figure._cachedRenderer
   2214                 bbox_inches = self.figure.get_tightbbox(renderer)

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/backends/backend_agg.pyc in print_png(self, filename_or_obj, *args, **kwargs)
    515 
    516     def print_png(self, filename_or_obj, *args, **kwargs):
--> 517         FigureCanvasAgg.draw(self)
    518         renderer = self.get_renderer()
    519         original_dpi = renderer.dpi

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/backends/backend_agg.pyc in draw(self)
    435             # if toolbar:
    436             #     toolbar.set_cursor(cursors.WAIT)
--> 437             self.figure.draw(self.renderer)
    438             # A GUI class may be need to update a window using this draw, so
    439             # don't forget to call the superclass.

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/artist.pyc in draw_wrapper(artist, renderer, *args, **kwargs)
     53                 renderer.start_filter()
     54 
---> 55             return draw(artist, renderer, *args, **kwargs)
     56         finally:
     57             if artist.get_agg_filter() is not None:

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/figure.pyc in draw(self, renderer)
   1491 
   1492             mimage._draw_list_compositing_images(
-> 1493                 renderer, self, artists, self.suppressComposite)
   1494 
   1495             renderer.close_group('figure')

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/image.pyc in _draw_list_compositing_images(renderer, parent, artists, suppress_composite)
    139     if not_composite or not has_images:
    140         for a in artists:
--> 141             a.draw(renderer)
    142     else:
    143         # Composite any adjacent images together

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/artist.pyc in draw_wrapper(artist, renderer, *args, **kwargs)
     53                 renderer.start_filter()
     54 
---> 55             return draw(artist, renderer, *args, **kwargs)
     56         finally:
     57             if artist.get_agg_filter() is not None:

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/axes/_base.pyc in draw(self, renderer, inframe)
   2633             renderer.stop_rasterizing()
   2634 
-> 2635         mimage._draw_list_compositing_images(renderer, self, artists)
   2636 
   2637         renderer.close_group('axes')

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/image.pyc in _draw_list_compositing_images(renderer, parent, artists, suppress_composite)
    139     if not_composite or not has_images:
    140         for a in artists:
--> 141             a.draw(renderer)
    142     else:
    143         # Composite any adjacent images together

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/artist.pyc in draw_wrapper(artist, renderer, *args, **kwargs)
     53                 renderer.start_filter()
     54 
---> 55             return draw(artist, renderer, *args, **kwargs)
     56         finally:
     57             if artist.get_agg_filter() is not None:

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/image.pyc in draw(self, renderer, *args, **kwargs)
    592         else:
    593             im, l, b, trans = self.make_image(
--> 594                 renderer, renderer.get_image_magnification())
    595             if im is not None:
    596                 renderer.draw_image(gc, l, b, im)

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/image.pyc in make_image(self, renderer, magnification, unsampled)
    840         return self._make_image(
    841             self._A, bbox, transformed_bbox, self.axes.bbox, magnification,
--> 842             unsampled=unsampled)
    843 
    844     def _check_unsampled_image(self, renderer):

/xxx/anaconda2/lib/python2.7/site-packages/matplotlib/image.pyc in _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification, unsampled, round_to_pixel_border)
    520                 alpha_channel = output[:, :, 3]
    521                 alpha_channel[:] = np.asarray(
--> 522                     np.asarray(alpha_channel, np.float32) * out_alpha * alpha,
    523                     np.uint8)
    524 

ValueError: operands could not be broadcast together with shapes (218,218) (100,100)